Injustice: Gods Among Us

Pretty simple, just do as the achievement says, beat every villain with Batman, even if they aren't in his rogue gallery like Doomsday.

Campaign villains beat while playing as Batman DOES count, afterwards I only had to beat a few more to get the achievement. If you're unsure, just keep track during the story mode, but you will definitely have to beat at least Ares, Grundy, Doomsday, Killer Frost, Sinestro, Black Adam and Harley separately.

All you have to do for the extras is load up a second controller in Multiplayer->Versus and beat the crap out of the 2nd player. You can also work on your Around the World and super moves achievement while doing this, which is what I recommend to save time.

UPDATE:

In story mode u battle deathstroke, bane, lex, joker, catwoman. That leave harley, grundy, ares, killer frost, doomsday, sinestro, and black adam that u have to battle.
Posted by OneManMafia86 on 19 Apr 13 06:25:03

FYRE 300 hit a lot of solid points, in that villains defeated in the campaign mode count toward the total... but if you're like me and you choose to go exploring through the game before doing the campaign, there's another way to hit a lot of villains quickly and contribute to another achievement.

Under the 'Battle' mode, there's a mode for 'villains only' and one for 'heroes only'. These need to be unlocked in the archives using Access Cards, but they're INCREDIBLY abundant, and you should get tons in no time simply by leveling up. You will also need to complete all of these to get the 'Ultimate Battler' achievement anyway, so if you go into this mode and select Batman, this will blast through the majority of the villains in the game. Just keep note of which ones you fought, and you should only have a couple more to clean up at the end. It doesn't QUITE kill two birds with one stone, but it severely injures them both, and makes them easier to kill seperately. ; )